Flank pain refers to discomfort or pain in the area extending from the lower ribs to the ilium. It is a prominent symptom of renal and upper urinary tract disease or trauma. The pain may vary from a dull ache to severe stabbing or throbbing, and can be unilateral or bilateral, constant or intermittent. Flank pain is typically aggravated by costovertebral angle (CVA) percussion and, in cases of urinary tract obstruction, by increased fluid intake or consumption of alcohol, caffeine, or diuretics. Position changes usually do not alleviate the pain, which often responds only to analgesics or treatment of the underlying disorder.

Pathophysiology

Flank pain generally arises from irritation, obstruction, inflammation, or trauma affecting the kidneys, ureters, or surrounding structures. Mechanisms include:

• Obstruction: stones or strictures causing distension of the renal pelvis or ureter

• Infection/inflammation: pyelonephritis, perirenal abscess

• Ischemia: renal infarction or thrombosis

• Trauma: blunt or penetrating injury to the kidneys or adjacent tissues

• Neoplastic processes: renal tumors or cystic disease

Signs and Symptoms

• Pain localized to the flank, possibly radiating to the lower abdomen, groin, or genitalia

• Unilateral or bilateral

• Colicky (stone-related) or dull and constant (infection, obstruction, trauma)

• Nausea and vomiting

• Hematuria (gross or microscopic)

• Fever and chills (if infection)

• Abdominal distention or palpable mass

• Hypoactive bowel sounds in severe cases

Emergency Interventions

Immediate steps in acute trauma or severe presentations:

1. Assess for flank mass, CVA tenderness, hematuria, Turner’s sign, and shock (tachycardia, cool clammy skin).

2. Establish IV access for fluid and medication administration.

3. Insert indwelling urinary catheter to monitor urine output and evaluate hematuria.

4. Obtain laboratory tests: CBC, electrolytes, blood typing and crossmatch.

5. Prepare for surgical or advanced interventions as indicated.

History Taking

When the patient is stable, collect detailed information:

• Onset: sudden vs. gradual

• Pattern and intensity: colicky vs. dull, intermittent vs. constant

• Precipitating or relieving factors: fluid intake, medications, activity

• Associated symptoms: dysuria, hematuria, urinary frequency, nocturia, tenesmus, fever, nausea, vomiting

• Past medical history: UTIs, renal disease, recent streptococcal infections, kidney stones

Physical Examination

• Inspection: palpable flank mass, abdominal distention, signs of trauma

• Palpation: CVA tenderness, abdominal rigidity, masses

• Percussion: CVA tenderness, dullness suggesting fluid or hematoma

• General: tachycardia, hypotension, signs of shock in trauma

• Other findings: fever, pallor, diaphoresis

Medical Causes of Flank Pain and Distinguishing Features

Special Considerations

• Administer analgesics as appropriate

• Monitor vital signs and strict input/output

• Diagnostic evaluation may include:

  • Urine and serum analysis

  • Excretory urography

  • Flank ultrasonography

  • CT scan

  • Voiding cystourethrography, cystoscopy

  • Retrograde ureteropyelography or cystography

Patient Counseling

• Educate on signs/symptoms to report (hematuria, fever, worsening pain)

• Advise on maintaining adequate fluid intake unless contraindicated

• Emphasize adherence to medications and follow-up appointments

Pediatric Pointers

• Children may not reliably describe flank pain

• Use transillumination to assess bladder distention or masses

• Common causes include obstructive uropathy, poststreptococcal glomerulonephritis, infantile polycystic kidney disease, nephroblastoma

References

1. Bande, D., Abbara, S., & Kalva, S. P. (2011). Acute renal infarction secondary to calcific embolus from mitral annular calcification. Cardiovascular Interventional Radiology, 34, 647–649.

2. Lopez, V. M., & Glauser, J. (2010). A case of renal artery thrombosis with renal infarction. Journal of Emergency Trauma and Shock, 3, 302.

3. Smith, R. P., & Ferrandino, M. N. (2012). Renal colic: evaluation and management. The New England Journal of Medicine, 367, 744–754.

4. McDougal, W. S., & Wein, A. J. (2018). Campbell-Walsh Urology, 12th Edition. Elsevier.

5. Nigam, V., & Sud, R. (2014). Flank pain: diagnosis and treatment strategies. Indian Journal of Urology, 30(3), 217–225.

6. Bagley, D. H., & Clayman, R. V. (2004). Urolithiasis and renal obstruction. The Lancet, 363, 491–501.

7. Kliegman, R., et al. (2020). Nelson Textbook of Pediatrics, 22nd Edition. Elsevier.

8. Hsu, R. K., & McCulloch, C. E. (2013). Acute kidney injury and flank pain: epidemiology and outcomes. Clinical Journal of the American Society of Nephrology, 8, 1075–1083.